1. Field of the Invention
The present invention relates to image-forming apparatuses having a vacuum and a fabrication method therefor.
2. Description of the Related Art
In a so-called image-forming apparatus in which a phosphor in an image display member is irradiated with an electron beam emitted from an electron source so that the phosphor emits light to display an image, the inside of an envelope having the electron source and the image display member must be kept at a high vacuum. This is because of the fact that if gases are generated in the envelope and the pressure is increased, the electron source is adversely affected depending on the type of gases, and the amount of electron emission is decreased. Thus, a bright image cannot be displayed.
The generated gases are ionized by the electron beam, and the ionized gases collide with the electron source because they are accelerated by an electric field and may damage the electron source. Furthermore, in some cases, a discharge may take place in the envelope, resulting in the apparatus breaking.
Generally, the envelope of an image-forming apparatus includes a plurality of glass components. In such a case, the components are joined to each other by glass frit or the like. Once the joining is completed, the pressure is maintained by a getter placed in the envelope. As such a getter, in a typical CRT, an alloy having Ba as a major constituent is employed. In the evacuated envelope, in which joining has been completed, the alloy is heated by passing an electric current or by high frequency irradiation so that an evaporated film is formed on the inner wall of the envelope, and thus gases generated inside are adsorbed and high vacuum conditions are maintained. For this purpose, an evaporative getter having a clean metal surface, such as Ba, is employed, which adsorbs evaporated gases by heating in a vacuum.
However, in a flat-display image-forming apparatus using an electron source in which many electron-emitting elements are disposed on a flat substrate, that has been recently under development, in comparison with the CRT, the ratio of the volume of the envelope to the area of the inner wall of the envelope emitting gases is substantially decreased. In the case of the comparable generation of gases, the pressure inside the envelope increases, and its adverse effect may become rather serious.
In the CRT, since the envelope has an ample inside wall surface in which the electron source or the image display member are not placed, the getter as described above can be mounted thereon by evaporation or the like. In the flat image-forming apparatus using electron-emitting elements, most of the inside surface area of the envelope is occupied by the electron source and the image-forming member. Therefore, if a getter as the evaporated film adheres thereto, inconveniences such as a short circuit may occur, and thus the position in which the getter is mounted is strongly restricted.
Generally, a spot such as a corner of the envelope is used for forming the getter film so that the getter material does not adhere to the region occupied by the image-forming member and the electron source (hereinafter referred to as xe2x80x9can image display regionxe2x80x9d). If the display area is increased more than a certain amount, it is not possible to secure an area of the evaporated getter film sufficient for the amount of emission gases in the envelope.
In order to overcome the above and to secure a sufficient area of the getter film, a method is disclosed in Japanese Patent Laid-Open No. 5-151916, in which, as shown in FIG. 2A, a wire getter 1008 is stretched tightly in the exterior of an image display region between a phosphor 1006 and a field emission element 1007 which are opposed to each other in an envelope 1005, for example, in the periphery of the envelope 1005, and by using the wire getter 1008, a getter film 1009 is formed by evaporation on the inner wall of the periphery. Another method is disclosed in Japanese Patent Laid-Open No. 4-289640, in which, as shown in FIG. 2B, on the side of a space between a faceplate 1014 (an image display member) and a rear plate 1012 (an electron-source substrate) constituting an envelope, a getter chamber 1015 having a getter material 1018 for forming a getter film in the envelope is attached. Alternatively, another method is disclosed in Japanese Patent Laid-Open No. 1-235152, in which a given space is provided between an electron-source substrate and a rear plate of an envelope, and a getter film is formed therein.
Additionally, in the thin (flat) image-forming apparatus, when the generation of gases in the vacuum envelope is treated, the pressure is easily increased locally. With respect to an image display apparatus having an electron-source substrate and an image display member, in an evacuated envelope, gases are generated in the image display region irradiated with an electron beam and by the electron source itself.
In the conventional CRT, since an image display member and an electron source are separated and there is a space between them for forming a sufficient getter film smoothly, gases generated from the image display member are widely diffused before reaching the electron source and a portion thereof is adsorbed by the getter film, and thus the pressure is not extremely increased at the electron source. Since a getter film is also provided around the electron source, the pressure is not strongly increased locally.
However, in the thin image-forming apparatus, since an image display member and an electron-source substrate are placed closely, gases generated from the image display member reach the electron source before being sufficiently diffused, resulting in a local pressure increase. In particular, in the center of the image display region, a higher local pressure increase is observed in comparison with the periphery, because the distance to the getter film is longer than the distance between the image display region and the electron-source substrate, and the gases cannot be diffused to the region where the getter film is formed. Therefore, the generated gases are ionized by electrons released from the electron source and are accelerated by an electric field formed between the electron source and the image display member, and thus the electron source may be broken or damaged.
In view of the above, a thin image-forming apparatus provided with a specific structure, that is, an image-forming apparatus in which a getter material is disposed in the image display region so that the generated gases are immediately adsorbed, is also disclosed. For example, in accordance with an apparatus disclosed in Japanese Patent Laid-Open No. 4-12436, with respect to an electron source having a gate electrode for supplying electrons for an electron beam, the gate electrode is composed of a getter material, and a field emission electron source having a conical protrusion as a negative electrode and a semiconductor electron source having a pn junction are described as examples. In accordance with a method disclosed in Japanese Patent Laid-Open No. 63-181248, with respect to a flat panel display having a structure in which an electrode, such as a grid, for controlling an electron beam is disposed between a cathode (negative electrode) group and a faceplate in an evacuated envelope, a getter material film is formed on the controlling electrode.
In U.S. Pat. No. 5,453,659, a structure is disclosed in which a getter is formed in the interstices of phosphors in the form of stripes on an image display member (anode plate). In this case, the getter is electrically isolated from the phosphors and a conductor which is electrically connected thereto, and the getter is activated by the irradiation with electrons emitted from the electron source by applying an appropriate electric potential, or by heating the getter by passing an electric current.
Meanwhile, in a thin image-forming apparatus, it is desirable to simplify the structure and fabrication method in view of production technology, production costs, and the like. Therefore, the fabrication of electron-emitting elements constituting the electron source must be achieved by the deposition of thin films and simple processes. When a large apparatus is fabricated, the fabrication must be achieved by a technique that does not require a vacuum apparatus, such as by printing.
A background technique for the present invention is disclosed in Japanese Patent Laid-Open No. 56-162447 in which a mixture of getter powder and a heat-resistant inorganic adhesive is used in an electron tube.
In Japanese Patent Laid-Open No. 10-12164, a technique is disclosed, in which a bulk getter is fixed using silver paste in a flat panel display device.
It is an object of the present invention to provide image-forming apparatuses in which getters are suitably placed, and to provide a suitable method for fabricating the same.
In accordance with the present invention, image-forming apparatuses have the following structures.
In one aspect, an image-forming apparatus includes a hermetically sealed container and a getter provided in the hermetically sealed container. The getter is fixed by an inorganic high polymer or a substance originating from the inorganic high polymer.
In another aspect, an image-forming apparatus includes a hermetically sealed container and a getter provided in the hermetically sealed container. The getter is fixed by a silicate adhesive or a substance originating from the silicate adhesive.
In another aspect, an image-forming apparatus includes a hermetically sealed container and a getter provided in the hermetically sealed container. The getter is fixed by a phosphate adhesive or a substance originating from the phosphate adhesive.
In another aspect, an image-forming apparatus includes a hermetically sealed container and a getter provided in the hermetically sealed container. The getter is fixed by a colloidal silica adhesive or a substance originating from the colloidal silica adhesive.
In another aspect, an image-forming apparatus includes a hermetically sealed container and a getter provided in the hermetically sealed container. The getter is fixed by a ladder silicone adhesive or a substance originating from the ladder silicone adhesive.
In another aspect, an image-forming apparatus includes a hermetically sealed container and a getter provided in the hermetically sealed container. The getter is fixed by a ladder silicone oligomer or a substance originating from the ladder silicone oligomer.
In another aspect, an image-forming apparatus includes a hermetically sealed container and a getter provided in the hermetically sealed container. The getter is fixed by an adhesive containing silicon-oxygen bonds.
In another aspect, an image-forming apparatus includes a hermetically sealed container and a getter provided in the hermetically sealed container. The getter is fixed by a solder or a substance originating from the solder.
In another aspect, an image-forming apparatus includes a hermetically sealed container and a getter provided in the hermetically sealed container. The getter is fixed by glass frit or a substance originating from the glass frit.
In another aspect, an image-forming apparatus includes a hermetically sealed container, a first member provided in the hermetically sealed container, and a getter fixed in contact with the first member. The fixed portion of the getter and a constituent of the first member form a solid solution.
In another aspect, an image-forming apparatus includes a hermetically sealed container and a getter provided in the hermetically sealed container. The getter constitutes a material getter member containing a non-evaporable getter, and the getter member is fixed at a cut-out section or a hole section of the getter member by an adhesive.
The cut-out section or the hole section may be formed by making a cut-out or a hole after the getter member is formed. The cut-out or the hole may be simultaneously made when the getter member is formed. The adhesive may be present in a region excluding the cut-out section or the hole section.
In another aspect, an image-forming apparatus includes a hermetically sealed container and a getter provided in the hermetically sealed container. The getter constitutes a material getter member, and the getter member is fixed at a cut-out section or a hole section of the getter member by an inorganic adhesive or a substance originating from the inorganic adhesive.
In another aspect, an image-forming apparatus includes a hermetically sealed container and a getter provided in the hermetically sealed container. At least a portion of the getter is present in an image-forming region in the hermetically sealed container, and the getter is fixed by an adhesive.
In another aspect, an image-forming apparatus includes a hermetically sealed container and a getter provided in the hermetically sealed container. The getter is provided both in an image-forming region and in a region excluding the image-forming region within the hermetically sealed container, and at least one fixed portion of the getter is provided in the region excluding the image-forming region.
In another aspect, an image-forming apparatus includes a hermetically sealed container and a getter provided in the hermetically sealed container. The getter is obtained by heating after a mixture containing a particulate getter material and an adhesive at a weight ratio of 10:1 to 20:1 is placed at a given position.
With respect to the structures of the present invention described above, the hermetically sealed container is preferably provided with an electron-emitting element. The hermetically sealed container is also preferably provided with an electrode for applying an electric potential in order to accelerate electrons emitted by the electron-emitting element. A potential difference of 5 kV or more is preferably applied between the electron-emitting element and the electrode during operation.
The inner space of the hermetically sealed container is preferably thin and flat. With respect to the inner space of the hermetically sealed container, a diagonal line parallel to the plane for forming an image is preferably 4.5 or more times as long as a length perpendicular to the plane for forming the image.
When the getter is in contact with wiring provided in the hermetically sealed container, the getter is preferably electrically connected to the wiring.
When the getter is provided in the vicinity of a phosphor, the getter is preferably provided in the interstices of a plurality of phosphors.
The getter may contain a powdered getter material having a particle diameter of 1 to 300 xcexcm.
In accordance with the present invention, a method for fabricating an image-forming apparatus includes the steps of bonding a non-evaporable getter in a hermetically sealed container, and degassing an adhesive used in the bonding step.
Preferably, the degassing step is a step of heating at temperatures of 250xc2x0 C. or more, or at temperatures of 350xc2x0 C. or more. Preferably, the degassing step is a step of heating at temperatures of 450xc2x0 C. or less, or at temperatures of 400xc2x0 C. or less.
Preferably, the degassing step is a step of heating for 1 hour or more.
When the temperature in the degassing step is low, heating is preferably performed for 3 hours or more, and when the temperature is high, heating is preferably performed for 3 hours or less. Preferably, heating is performed for less than 30 hours.
The degassing step is preferably started after the adhesive-curing step is started.
The adhesive used in the fabrication method described above is preferably an inorganic adhesive.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.